1. Field of the Invention
This invention is directed to an electronic ballast system for fluorescent or gas discharge tubes. In particular, this invention relates to automatic gain controlled ballast systems for fluorescent tubes. Still further, this invention relates to an electronic ballast system which limits the voltage output to fluorescent or gas discharge tubes when the output voltage of the power source increases. This invention limits the output voltage of the electronic ballast system and substantially reduces such when the gas discharge tube or fluorescent tube is electrically removed from the overall circuit. More in particular, this invention pertains to a no load protection transformer being series coupled to an induction circuit for preventing the generation of voltages above a predetermined value when the gas discharge or fluorescent tube is electrically removed from the circuit. More in particular, this invention relates to an electronic ballast system where a primary winding of a no load protection transformer forms a variable inductance which is inversely proportional to the magnitude of power delivered to the gas discharge or fluorescent tube.
Still further, this invention directs itself to a transistor switching mechanism which is feedback coupled to an induction circuit for establishing a regulated current for a gas discharge tube independent of the gain of a transistor used in a particular ballast system unit. Additionally, this invention pertains to an electronic ballast system where there is provided a transistor switching network including a regulation control circuit for maintaining the power output of a gas discharge or fluorescent tube at a predetermined and substantially constant value.
Further, this invention directs itself to an electronic ballast system having a toroidal transformer to provide a predetermined variable inductance for regulating a power output to the gas discharge or fluorescent tube. Still further, this invention relates to an electronic ballast system which is transistorized and where the current gain of various transistors range over a wide value range from one system unit to another and provides for electrical circuitry which will maintain the gas discharge tube light output fluctuation to a minimum tolerance value.
2. Prior Art
Electronic ballast systems for gas discharge or fluorescent tubes are known in the art. However, in some prior art electronic ballast systems, removal of the gas discharge or fluorescent tube from the ballast circuit causes excessive voltage outputs to the gas discharge or fluorescent tubes. This condition can have a deleterious effect to the operating life of the particular tube or set of tubes utilized in a particular ballast system.
Other prior art systems do not provide for a no load protection transformer being coupled to an induction circuit of such electronic ballast systems for preventing the generation of voltages above predetermined values when the gas discharge or fluorescent tubes are electrically decoupled from the ballast circuit. Such prior art systems do not have the capability of providing a variable inductance which is inversely proportional to the magnitude of the power delivered to the gas discharge or fluorescent tubes. Thus, such prior art systems do not allow a limited voltage to be generated by control of the collector current of the ballast transistor responsive to load conditions, as is seen in the subject invention concept.
In other prior art electronic ballast systems, the light output of the gas discharge tubes are highly dependent upon the gain of the transistors used in the circuits. In such prior art systems, where the transistor gains between one unit and another vary over a large value, the light output from the gas discharge tube may fluctuate by excessive amounts. In such prior art systems, additional circuitry must be added to such electronic ballast systems to maintain the light output fluctuation as constant as possible between differing units.